Locomotive  Testing 


. . AT  • . 

PURDUE  UNIVERSITY. 


i 


LAFAYETTE,  INDIANA. 
1894. 


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PRINCIPLES 

UNDERLYING  THE  PLAN  OF  MOUNTING. 

[ See  Plate  1. 1 


The  plan  of  mounting  a locomotive  for  experimental  purposes,  in 
its  inception,  involved  (i)  supporting  wheels  carried  by  shafts  running 
in  fixed  bearings,  to  receive  the  locomotive  drivers  and  to  turn  with 
them;  (2)  brakes  which  should  have  sufficient  capacity  to  absorb  con- 
tinuously the  maximum  power  of  the  locomotive,  and  which  should  be 
mounted  on  the  shafts  of  the  supporting  wheels;  (3)  a traction  dynamo- 
meter of  such  form  as  would  serve  to  indicate  the  horizontal  moving 
force  and  at  the  same  time  allow  but  a slight  horizontal  motion  of  the 
engine  on  the  supporting  wheels. 

Assume  an  engine,  thus  mounted,  to  be  running  in  forward  motion 
the  supporting  wheels,  the  faces  of  which  constitute  the  track,  revolving 
freely  in  rolling  contact  with  the  drivers.  The  locomotive  as  a whole, 
being  at  rest,  the  track  under  it  (the  top  of  the  supporting  wheels)  is 
forced  to  move  backward.  If  now  the  supporting  wheels  be  retarded  in 
their  motion,  as  for  example  by  the  action  of  friction  brakes,  the  engine 
must  as  a result  tend  to  move  off  them.  If  they  be  stopped,  the  drivers 
must  stop  or  slip.  Whether  the  resistance  be  great  or  small,  the  force 
which  is  transmitted  from  the  driver  to  the  supporting  wheel  to  over- 
come the  resistance,  will  reappear  as  a stress  in  the  draw-bar  which 
alone  holds  the  locomotive  to  its  place  upon  the  supporting  wheels. 
The  dynamometer  constitutes  the  fixed  point  with  which  the  draw-bar 
connects  and  serves  to  measure  stresses  transmitted. 

It  is  evident  from  these  considerations  that  the  tractive  power  of 
such  a locomotive  may  be  increased  or  diminished  by  simply  varying 
the  resistance  against  which  the  supporting  wheels  turn,  and  that  the 
readings  of  the  traction  dynamometer  will  always  serve  as  a basis  for 
calculating  work  done  at  the  draw-bar.  It  was  believed  that  a locomotive 


4 


thus  mounted  could  be  run  either  ahead  or  aback  under  any  desired 
load  and  at  any  speed;  that,  while  thus  run,  its  performance  could  be 
determined  with  a degree  of  accuracy  and  completeness  far  excelling 
•that  which  it  is  possible  to  secure  under  ordinary  conditions  of  the  road; 
and  that  the  whole  apparatus  would  be  extremely  useful  to  students 
in  steam  engineering.  It  was  not  thought  that  every  condition  of  the 
track  would  be  perfectly  met,  but  it  was  expected  that  the  results  ob- 
tained would  prove  valuable  in  extending  a knowledge  of  locomotive 
performance.  How  far  these  conceptions  were  justifiable,  the  sequel  will 
show. 


FROM  A PHOTOGRAPH  OF  THE  FIRST  PLANT. 


THE  DEVELOPMENT  OF  THE  PLAN  OF 
MOUNTING. 


The  matter  of  having  a locomotive  mounted  for  the  purpose  of 
experiment  was  discussed  at  Purdue  early  in  the  year  of  1890  and  it  was 
so  well  received  that  in  May  1891  an  order  was  given  the  Schenectady 
Locomotive  Works  for  a 17"  x 24"  eight- wheeled  engine.  The  details  of 
the  mounting  were  worked  out  during  the  two  months  following.  In 
September  the  locomotive  had  been  delivered  and  it  was  in  operation 
before  the  close  of  the  year. 

This  plant,  which  is  believed  to  be  the  first  of  its  kind,  is  described 
in  detail  in  a paper  entitled  “An  Experimental  Locomotive,”  which  was 
read  before  the  American  Society  of  Mechanical  Engineers  at  the  San 
Francisco  meeting  in  May  1892.  A second  paper,  “Tests  of  the  Loco- 
motive at  the  Laboratory  of  Purdue  University,”  before  the  same  society 
a year  later,  gives  the  result  of  twenty  efficiency  tests  which  were  made 
during  the  winter  of  1892-93.  Besides  the  work  involved  by  these 
elaborate  tests,  attention  was  given  to  various  matters  ol  minor  import- 
ance, among  which  may  be  mentioned  the  counterbalance  problem.  In 
the  course  of  this  latter  work,  the  fact  that  a driver  through  the  action  of 
its  counterbalance,  will  under  certain  conditions  actually  leave  the  track 
was  demonstrated  by  passing  a wire  under  the  moving  wheel;  wires 
thus  passed  at  high  speed,  came  out  with  a portion  of  their  length  untouched 
by  the  wheel.  It  was  also  shown  that  a long  pipe-connection  for  an  indicator, 
such  as  is  generally  used  in  road  tests,  tends  to  enlarge  the  card  given 
by  the  indicator,  as  the  speed  of  the  engine  increases. 

During  the  latter  part  of  1893  a very  complete  series  of  fourteen 
efficiency  tests  were  run.  These  were  made  under  full  throttle  and  some  of 
them  at  high  speeds,  the  indicator  showing  from  300  to  700  horse- 
power. The  observed  data  obtained  from  these  tests  was  of  a very 
complete  character  and  much  was  expected  of  it;  but  it  was  destined  to 
serve  no  useful  purpose. 


6 


On  the  23d  of  January,  1894  the  Engineering  Laboratory  was  burned. 
All  experimental  data  which  had  not  been  published,  went  up  in  smoke, 
and  the  locomotive  went  down  in  the  wreck.  The  fire  entailed  a heavy 
burden  of  labor  and  expense.  But  with  the  new  responsibilities 
which  it  brought,  there  came  also,  new  opportunities.  All  details  of 
the  mounting  mechanism  were  most  carefully  reviewed,  and  every 
fragment  of  experience  was  made  to  serve  a useful  purpose  in  the  design 
of  a new  plant.  The  damaged  locomotive  was  extracted  from  the  ruin  and 
delivered  to  the  P.  C.  C.  & St.  L.  R.  R.  Co.,  at  Indianapolis  for  repairs. 
Though  but  four  months  have  passed  since  the  fire,  the  new  work  is  now 
complete  and  the  reconstructed  engine  is  in  position.  The  following 
pages  will  serve  to  indicate  the  character  of  the  new  plant. 


FROM  A PHOTOGRAPH  AFTER  THE  FIRE. 


THE  NEW  PLANT. 


A comparison  of  Plates  I.  and  II.  with  the  published  drawings  of  the 
original  plant,  to  which  reference  has  already  been  made  will  disclose 
important  changes.  The  new  plant  as  shown  by  the  accompanying 
plates,  occupies  a building  especially  planned  to  receive  it,  and  it  is 
arranged  for  the  accommodation  of  any  locomotive, either  steam  or  electric. 
The  dotted  outline  in  Plate  I.  is  to  the  scale  of  the  University’s  locomo- 
tive “Schenectady.” 


THE  WHEEL  FOUNDATION. 

By  reference  to  Plates  I.  and  II.  it  will  be  seen  that  there  is  provided  a 
wheel  foundation  of  nearly  twenty-five  feet  in  length.  This  is  more 
than  sufficient  to  include  the  driving-wheel  base  of  any  standard  eight, 
ten,  or  twelve-wheeled  engine.  For  engines  having  six  wheels  coupled, 
a third  supporting  axle  will  be  added  to  those  shown,  and  for  engines 
having  eight  wheels  coupled,  four  new  axles  having  wheels  of  smaller 
diameter  than  those  shown,  will  be  used. 

The  wheel  foundation  carries  cast-iron  bed-plates  to  which  are 
secured  pedestals  for  the  support  of  the  axle  boxes.  The  lower  flanges 
of  the  pedestals  are  slotted,  and  the  bed-plates  have  threaded  holes 
spaced  along  their  length.  By  these  means,  the  pedestals  may  be  ad- 
justed to  any  position  along  the  length  of  the  foundation. 

The  boxes  in  use  at  present,  are  plain  babbitted  shaft  bearings,  and 
between  each  bearing  and  its  pedestal,  a wooden  cushion  is  inserted.  A 
bearing  has  been  designed  for  use  in  some  special  experiments,  which 
provides  for  the  suspension  of  the  axle  from  springs,  but  this  bearing 
has  not  yet  been  used. 

The  outer  edges  of  the  wheel  foundation  are  topped  by  timbers  to 
which  the  brake  cases  are  anchored.  The  brakes  which  absorb  the 
power  of  the  engine,  are  the  ones  which  were  used  in  the  original  plant. 
They  are  constructed  upon  a principle  developed  by  Professor  Geo.  I. 
Alden,  and  their  capacity  and  wearing  qualities  are  beyond  question. 


8 


The  load  upon  them  is  controled  by  varying  the  pressure  of  water  which 
circulates  through  them  and  carries  away  the  heat.  The  water  pressure 
acts  upon  stationary  copper  plates  which  are  forced  against  a moving  cast 
iron  disc  thereby  creating  friction.  No  provision  is  made  for  determining 
the  load  upon  each  brake,  but  the  loads  may  be  equalizedjby  equalizing 
the  flow  and  pressure  of  the  cooling  water.  The  sum  of  these  loads  plus 
the  friction  of  the  axles  in  their  boxes,  makes  up  the  sum  total  of  work 
to  be  done;  this  work  must  be  given  out  from  the  locomotive  drivers.  It 
all  reappears  in  the  form  of  draw-bar  stress  and  its  value  is  shown  by 
the  traction  dynamometer.  An  elaborate  system  of  piping  (not  shown 
on  plates)  provides  for  the  circulation  of  the  cooling  water  for  the 
brakes,  at  whatever  point  along  the  length  of  the  foundation  they  may 
be  located. 

THE  TRACTION  DYNAMOMETER. 

The  vibrating  character  of  the  stresses  to  be  measured,  makes  the 
design  of  the  traction  dynamometer  a matter  of  some  difficulty.  The 
dynamometer  of  the  original  plant  consisted  of  an  inexpensive  system 
of  levers  attached  to  a heavy  frame  work  of  wood,  the  vibrations  being 
controled  by  dashpots.  In  the  present  construction,  wood  as  a support 
is  entirely  abandoned  and  a massive  brick  pier,  well  stayed  with  iron 
rods,  has  been  substituted.  The  dynamometer  itself  consists  of  the 
weighing  head  of  an  Emery  testing  machine,  the  hydraulic  support 
of  which  is  capable  not  only  of  transmitting  the  stress  it  receives,  but 
also  of  withstanding  the  rapid  vibrations  which  the  drawbar  transmits  to 
it.  The  apparatus  is  of  30,000  pounds  capacity. 

In  view  of  the  enormous  force  which  a locomotive  is  capable  of 
exerting,  it  would  appear  at  first  sight,  that  an  error  of  50  or  even  100 
pounds  in  the  determination  of  draw-bar  stresses  would  be  of  slight 
consequence,  and  that  great  accuracy  in  this  matter  is  not  required. 
Under  some  conditions  this  conclusion  is  correct  but  under  others  it 
is  far  from  true.  The  work  done  at  the  draw-bar  is  the  product  of  the 
force  exerted,  multiplied  by  the  space  passed  over;  if  the  force  exerted 
be  great  and  the  speed  low,  a small  error  in  the  draw-bar  stress  is  not  a 
matter  of  great  importance;  but  if  the  reverse  conditions  exist,  if  the 
speed  be  high  and  the  draw-bar  stress  low,  then  it  is  absolutly  necessary 
that  the  draw-bar  stress  be  determined  with  great  accuracy.  Moreover, 


9 


high  speeds  necessarily  involve  low  draw-bar  stress.  A locomotive 
which  at  ten  miles  an  hour  may  pull  12,000  pounds,  will  have  difficulty 
when  running  sixty  miles  per  hour,  in  maintaining  a pull  of  2,500  pounds. 
These  conditions  have  prompted  the  Purdue  authorities  to  make  ex- 
traordinary efforts  to  secure  accurate  measurements  at  the  draw-bar,  and 
they  serve  as  a sufficient  justification  of  the  heavy  expenditure  involved 
in  the  purchase  of  the  Emery  machine. 

As  is  well  known,  the  arrangement  of  the  hydraulic  support  of  the 
Emery  testing  machine,  permits  the  weighing  scale  to  be  at  any  con- 
venient distance  from  the  point  where  the  stresses  are  received.  Plates 
I.  and  II.  show  only  the  receiving  end  of  the  apparatus.  The  draw-bar 
connects  with  this  apparatus  by  a ball  joint  which  leaves  its  outer  end 
free  to  respond  to  the  movement  of  the  locomotive  on  its  springs.  A 
threaded  sleeve  allows  the  draw-bar  to  be  lengthened  or  shortened  for  a 
final  adjustment  of  the  locomotive  to  its  position  upon  the  supporting 
wheels;  and,  finally,  to  meet  the  proportions  of  different  locomotives,  pro- 
vision is  made  for  a vertical  adjustment  of  the  entire  head  of  the  machine 
upon  its  frame. 


THE  SUPERSTRUCTURE. 

Plates  III.  and  IV.  show  the  arrangement  of  floors.  The  “visitors’ 
floor”  (Plate  IV.)  and  the  fixed  floors  adjoining,  are  at  the  level  of  the 
rail.  The  open  space  over  the  wheel  foundation  is  of  such  dimensions 
as  will  easily  accommodate  an  engine  having  a long  driving-wheel  base, 
moveable  or  temporary  floors  being  used  to  fill  in  about  each  different 
engine,  as  may  be  found  convenient.  The  temporary  flooring  shown,  is 
that  employed  for  the  Purdue  Locomotive. 

The  level  of  the  “tender  floor”  is  at  a sufficient  height  above  the  rail 
to  serve  as  a platform  from  which  to  fire.  At  the  rear,  is  a run-way 
leading  to  the  coal  room,  the  floor  of  which  is  somewhat  lower  than  the 
tender  floor.  A platform  scale  is  set  flush  with  the  floor  at  the  head  of 
the  run-way.  During  tests  the  scale  is  used  for  weighing  the  coal  which 
is  delivered  to  the  fireman. 

The  feed-water  tank,  from  which  the  injectors  draw  their  supply,  is 
shown  in  the  lower  right-hand  corner  of  Plate  IV.  Above  this  supply 
tank,  are  two  small  calibrated  tanks  so  arranged  that  one  may  be  filled 
while  the  other  is  discharging. 


o 


The  steam  pump  shown  on  the  visitors’  floor  is  for  the  purpose  of 
supplying  water  under  pressure,  to  the  friction  brakes  which  load  the 
engine. 

The  conditions  under  which  the  engine  is  operated  are  at  all  times 
within  the  control  of  a single  person  whose  place  is  just  at  the  right  of 
the  steps  leading  to  the  tender  floor.  From  this  position  he  can  see  the 
throttle  and  reverse  lever,  and  observe  all  that  goes  on  in  the  cab.  At 
his  right  is  the  dynamometer  scale-case  wherein  is  shown  the  load  at 
the  draw-bar;  in  front  are  the  gages  giving  the  water  pressure  on  the 
brakes;  and  under  his  hand  are  the  valves  controling  the  circulation  of 
water  through  the  brakes. 

No  attempt  has  been  made  in  these  drawings  to  show  small  accessory 
apparatus,  neither  does  it  seem  necessary  to  give  an  enumeration. 

THE  BUILDING. 

Plate  V.  presents  several  views  of  the  locomotive  building.  The 
entrance  door,  which  opens  upon  the  visitors’  floor,  is  shown  in  the 
south  elevation.  It  is  approached  from  the  general  laboratory,  150  feet 
away. 

The  north  and  west  elevations  show  the  roof  construction,  whereby 
the  upper  end  of  the  locomotive  stack  is  made  to  stand  outside  of  the 
building.  The  roof  sections  shown  may  be  entirely  removed,  and  a door 
in  the  cross-wall,  which  extends  between  the  removable  roof  and  the 
main  roof,  provides  ample  height  for  the  admission  of  the  locomotive  to 
the  building.  A window  in  this  door  (Plate  IV.)  serves  to  give  the  fire- 
man a clear  view  of  the  top  of  the  locomotive  stack  from  his  place  in  the 
cab,  a condition  which  is  essential  to  good  work  in  firing.  Above  the 
stack  is  a pipe  to  convey  the  smoke  clear  of  the  building*  To  meet  a 
change  in  the  location  of  the  stack,  this  pipe  may  be  moved  to  any  posi- 
tion along  the  length  of  the  removable  roof.  It  is  proposed  to  embody 
in  this  pipe,  a simple  form  of  cinder  trap  which  will  catch  and  hold  the 
sparks  thrown  out  by  the  locomotive. 

The  plan  of  the  building  ( Plate  V.)  shows  the  arrangement  of  tracks 
for  the  locomotive,  and,  of  those  used  for  supplying  coal. 


I I 


THE  PURDUE  RAILROAD. 


In  the  process  of  establishing  the  first  plant,  it  was  necessary  to 
move  the  85000-pound  locomotive, “Schenectady,”  across  wheat  fields  and 
pastures,  for  a distance  of  one  and  a quarter  miles.  Now  Purdue  has  a 
track  of  its  own  connecting  the  locomotive  laboratory  with  the  railroads 
of  the  country.  Locomotives  may  now  be  received  and  delivered  with- 
out difficulty.  For  example,  when  the  University  engine  was  re- 
turned after  being  repaired  at  Indianapolis,  it  was  put  under  its  own 
steam  and  backed  in  on  the  Purdue  track,  directly  to  its  place  over  the 
supporting  wheels  of  the  testing  plant.  The  track  will  also  serve  to 
bring  in  supplies  of  every  sort. 


ALDEN  FRICTION  BRAKE. 
(one-half  OF  CAEE  REMOVED./ 


Wooi'Roo'm 


THE  BALDWIN  FOUR-CYLINDER  COMPOUND. 


The  general  engineering  laboratory  of  the  University,  as  a building, 
is  quite  distinct  from  the  plant  which  has  thus  far  been  described,  but 
it  also  offers  some  important  facilities  for  locomotive  testing.  In  this 
laboratory  will  be  the  engines  of  a 9^  and  r6  by  18  Vouclain  compound 
locomotive.  These  engines  will  be  fitted  with  a fixed  frame  similar  to 
that  of  a stationary  engine,  and  will  be  mounted  upon  a foundation. 
Steam  will  be  supplied  them  from  the  laboratory  boilers,  their  exhaust 
will  be  piped  to  a Wheeler  condenser,  and  they  will  be  run  under  the 
load  of  a friction  brake.  This  apparatus  will  furnish  opportunities  for  a 
careful  experimental  study  of  this  type  of  compound  engine,  and  also  of 
some  of  the  questions  affecting  other  forms  of  compound  locomotives. 


FLOOR  PLAN  OF  THE  ENGINEERING  LABORATORY. 


< 

J 

Plh 


Locomotive  Laboratory.  PLATE  III  Purdue  University. 


Locomotive  Laboratory.  PLATE  IV  Purdue  University. 


■Nor\H  X\«v<A\o«  W*s,\tVtvftVi6n 

LOCOMOTIVE  LABORATORY.  Pl,ATE  V PURDUE  UNIVERSITY. 


